The use of solar energy for heating buildings or other enclosures has been known for centuries. A glass window and a living room rug can act as a solar heat collector. A green house and an outdoor swimming pool are other examples of solar heat collectors. The basic elements necessary for solar heat collection are an energy absorbing body within an enclosed area and a light admitting medium which allows solar radiation to enter the enclosed area and strike the energy absorbing body without allowing heat radiation to escape from the enclosed area. Nearly any nonreflective object will act as an energy absorber and any transparent or translucent object such as a plate of glass or a body of water will allow light to pass and will retain heat. The focus of solar heat collective inventions in recent years has been on improving the efficiency of these basic solar heat collection elements and in adapting solar heat collectors to conventional heating uses.
Lof, U.S. Pat. No. 2,680,565, discloses a solar heating system using a series of transparent and reflective plates with blackened lower surfaces. The glass plates are mounted on a roof and are protected from hail by a wire screen positioned above the plates. Air between the plates is in fluid communication with the conventional forced air heating system in the house.
Thomason, U.S. Pat. No. 3,369.539, discloses a solar heat collector located on an inclined surface wherein a mesh material is located inside a granular absorber material to prevent the granular material from creeping down the inclined surface.
Keyes, et. al., U.S. Pat. No. 3,946,720, discloses a solar heat collector in which a conditioning air flow is directed over a quantity of heat retaining material positioned within a baffle arrangement located beneath the glass face of the collector.
Loth, U.S. Pat. No. 4,154,220, discloses a solar heat collector enclosed within a rectangular box shaped housing. Conditioning air introduced at one end of the box is passed over a corrugated foam absorber and discharged from the opposite end of the box.
Lof, U.S. Pat. No. 4,072,142, discloses a solar heat collector which employs a corrugated screen located in an air gap beneath the absorber plate to increase the heat absorption of the conditioning air which is forced through the air gap.
Although the art discloses a number of different solar heat collectors adapted for residential heating, the basic functional elements of the heat collector remain unchanged. A problem in the efficiency of these devices has been that a substantial amount of light is reflected by the absorber and lost through the transparent medium. A means for redirecting this reflected light back to the absorber surface would improve the efficiency of any heat collector. Other problems with solar heat collectors have been their bulkiness and high cost.